[Histonet] Formalin filtering, reuse, expiration date questions

Rene J Buesa rjbuesa <@t> yahoo.com
Tue May 10 15:56:03 CDT 2011

This is more a concern than an answer: if you filter used formalin to eliminate any tissue remnants/contaminants left from the previous usage, you will be dealing with a formalin solution of LESS than 4% because some of the formaldehyde (methylene-glycol) has been retained in the tissues.
Unless you reconstitute the formalin (adjusting the concentration to 4%) theoretically you will end with a close to 0% formalin.
How do you deal with this issue?
René J.

From: "Morken, Timothy" <Timothy.Morken <@t> ucsfmedctr.org>
To: "histonet <@t> lists.utsouthwestern.edu" <histonet <@t> lists.utsouthwestern.edu>
Sent: Tuesday, May 10, 2011 3:55 PM
Subject: Re: [Histonet] Formalin filtering, reuse, expiration date questions

For those using formalin filtering to recycle formalin (i.e. Creative Waste Solutions formalin filtering unit or other methods), how have you liked it?

How many times do you reuse the formalin (and how do you tell?!)

How do you handle an expiration date for the filtered formalin?

For those using the Creative Waste unit, how well does the assay work for determining concentration?

Thanks for any and all info!!

Tim Morken
Supervisor, Histology, IPOX
UC San Francisco Medical Center

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